He was Artistic Director of the University College Players Guild from 1967 to 1968,[1] and received the McAndrew Award for his contributions to campus drama (which included his own adaptation of Joseph Heller's Catch-22 and the Canadian premiere of Arthur Miller's Incident at Vichy).

[3] In 2009 his play, The Alchemist of Cecil Street, starring Ron Orbach, Bryan Cranston and Ed Asner was produced by The Famous Radio Ranch.

In 2010 The Famous Radio Ranch followed up with a production of Dennis's play "Tolstoy Was Never There" starring Kevin Dunn, Ross Benjamin, Ron Orbach, Rose Abdoo, Ed Begley, Jr., John O'Hurley, Leila Birch, Kim Eveleth, Becky Bonar.

In 1963, Dennis made his professional stage debut at the Red Barn Theatre in Jackson's Point, Ontario playing Dr. Einstein in Arsenic and Old Lace and Simon Bliss in Hay Fever.

[1] In 2011, he returned to the boards playing Gregory Wagner for the Open Fist Theater Company in their production of Room Service by Murray and Boretz, which the Los Angeles Times described as a "superb revival".

Later that year he played Carlton Fitzgerald opposite Catherine Hicks in Moss Hart's Light Up the Sky at the JRTN in Las Vegas.

It was directed by Charles Haid and produced by Racquel Lehrman at the Zephyr Theater in Los Angeles with Michael Laskin as Franz Altman.

Author George Anthony wrote that Charles Dennis "was a talented young hotshot who wanted to do it all: write, produce, direct, star", and that he "worked as an entertainment writer for Toronto Telegram".

[1] In 2002, Dennis wrote three articles for the Calendar section of the Los Angeles Times about Ivor Novello, Phil Gersh, and Julian Fellowes.

In 1969 while living in London, Dennis adapted his play, Aztecs and Orange Juice, for ATV and appeared in it opposite Derek Fowlds and Cheryl Kennedy.

[20] Also in 1984 he co-authored a screenplay of his novel The Next-to-Last Train Ride for a film which was directed by Richard Lester and released under the title Finders Keepers.

[18] In 2010 he wrote and directed The Favour of Your Company starring Carolyn Seymour, Neil Dickson and Ron Orbach, which was shown at the BAFTA/LA Short Film Showcase.

The first season consisted of ten episodes, and series guest stars included Patty McCormack, Rick Podell, Kim Delgado, Lou Wagner, Patrick Pinney, and Nicole Ansari.

In 2018, Dennis wrote and directed the film, Barking Mad, which starred Neil Dickson, Michael Swan, Patty McCormack, Edward Asner, Loren Lester, Mary Stavin, and Fred Melamed.

In 2022, Dennis wrote and directed the feature film "Deadly Draw", which starred Brent Huff, Ulrika Vingsbo, Jack Maxwell, Fred Melamed, Gail O'Grady, Jeffrey Byron, Patty McCormack and Ed Asner (in his final screen appearance).